1. Field of the Invention
The present invention relates to a treatment method for eyes, and more particularly, to a method for burying an implant in the choroid.
2. Description of the Related Art
Many inflammatory diseases or proliferative diseases in a posterior segment of an eyeball, e.g., uveitis, diabetic retinopathy, proliferative vitreoretinopathy, macular degeneration, and others are serious disorders that require medication over a long period of time.
When carrying out systemic administration of medicines with respect to such a disorder, the administration of a large amount of medicines is required, and hence a systemic side-effect is concerned. Further, when carrying out instillation of ophthalmic drugs, a distance for the drug to reach a retina or a choroid lesion is long, there is a problem of an influence of tears or corneal permeability, and hence exercising an effective action is difficult.
Therefore, it is considered that administration of a medicine using a sustained release drug implant is suitable for a treatment of a posterior eye segment.
Here, as a sustained release system for a steroid, it has been reported that administration of dexamethasone or fluocinolone to a vitreous body is effective for a treatment of uveitis (Dexamethasone sustained drug delivery implant for the treatment of severe uveitis. Author: Jaffe G J, Pearson P A, Ashton P, Volume:20 Issue:4, Page:402-3 Year:2000 Source: Retina, Fluocinolone acetonide sustained drug delivery device to treat severe uveitis. Author: Jaffe G J, Ben-Nun J, Guo H, Dunn J P, Ashton P, Volume:107 Issue:11, Page:2024-33 Year:2000 Source: Ophthalmology). These sustained release drugs have compositions similar to that of an antiviral drug, but an antiviral drug implant may cause serious complications such as intravitreous hemorrhage, retinal detachment, intraocular inflammation, and others in some cases, and hence actually using such an implant for treatments is still difficult.
Further, it has been recently reported that sustained release from a sclera triggers an effective action of a drug to the posterior eye segment, and it has been informed that sustained release of a betamethasone phosphate from the sclera effectively acts on a vitreous body, a retina, or a choroid (Biodegradable intrascleralimplant for sustained intraocular delivery of betamethasone phosphate. Author: Okabe J, Kimura H, Kunou N, Okabe K, Kato A, Ogura Y, Volume:44 Issue:2, Page:740-4 Year:2003 Source: Invest Ophthalmol Vis Sci, Intraocular tissue distribution of betamethasone after intrascleral administration using a non-biodegradable sustained drug delivery device. Author: Okabe K, Kimura H, Okabe J, Kato A, Kunou N, Ogura Y, Volume:44 Issue:6, Page:2702-7 Year:2003 Source: Invest Ophthalmol Vis Sci).
However, since a distance between the sclera and the retina is too long to impregnate with a drug, providing a sufficient medicinal effect to the retina or the vitreous body on the inner side thereof is relatively difficult.
On the other hand, to exert an action of the drug to the retina or the vitreous body, it is considered that effecting sustained release of the drug from the choroid that is immediately adjacent to the retina is further effective. If the sustained release of the drug is performed from the choroid, an amount of the drug can be reduced, which is advantageous in terms of side-effects. Therefore, enabling implanting the betamethasone phosphate into the choroid is considered to be more preferable.
Here, as literatures concerning such a technology, there are a booklet of International Publication No. 2006/093758 and U.S. Pat. No. 5,869,079. These literatures describe burying an implant into the choroid.
However, an operation of burying an implant into the choroid is not easy. Although the choroid is a tissue placed between the sclera and the retina, the retina is an important tissue including a photoreceptor cell, a bipolar cell, a ganglion cell, a Müller cell, and others, and hence the closest attention must be paid in the operation for the choroid to avoid damages to the retina.
However, since the choroid is generally a thin membrane having a thickness of approximately 0.3 mm in case of a human and tensile force functions on the outer side due to an ocular pressure, an operation of forming a pocket utilized to insert an implant into the choroid without damaging the retina is very difficult, and a technology that facilitates this operation has not been found yet.